1. Technical Field
The present invention relates to electrically powered motors that are installed in vehicles.
2. Description of the Related Art
As a device for assisting automotive vehicle driving operations, hydraulic power steering, with which the operation of the steering wheel is assisted by means of hydraulic pressure generated by a pump run by engine output power, has traditionally been employed. In recent years, meanwhile, electric power assisted steering (abbreviated “EPAS” hereinafter), with which steering wheel operation is assisted by a motor rotationally powered by a vehicle on-board battery, has come into use. This latter power steering system, whereby engine power loss is low compared to systems that use the engine's rotation to generate hydraulic pressure, is receiving attention for its efficiency. In the motors employed in such EPAS systems, a diverse variety of electronic components that serve to realize high-precision motor control is surface-mounted onto a circuit board.
Among the electronic components for realizing high-precision control, Hall-effect sensors in particular, for detecting the rotational position of the poles of the magnetic-field producing magnet(s) in the rotor section of the motor, are accurately disposed in predetermined areas to detect the rotational position of the field magnet poles with high precision. Accurately disposing the Hall sensors enables efficient control of the armature current, whereby the efficiency with which the motor is driven is thus improved. Consequently, in motors that use Hall-effect sensors, adjustment of the position of the sensing elements is paramount. Nevertheless, in motors to date, low-cost, sufficiently exact locating of the Hall-effect sensors has not been achieved.
Moreover, demands are for automotive vehicles that run in good order over the long term. Consequently, high reliability is in turn being demanded of EPAS motors as one of the mechanical components of more reliable, longer-lasting vehicles. For that reason, in motors used in devices for assisting vehicle driving operations, the electronic components should be mounted firmly onto the circuit board so that not even one will come loose and fall off. Yet there has been a need to maintain high motor reliability also by secondary measures against adverse consequences in the rare event an electronic component should come loose and fall off. With motors to date, however, no motor in which such secondary measures have been implemented has existed.